Risk Factors of Shingles

An Overview of Shingles Risk Factors
Shingles is a condition caused by the varicella-zoster virus, which is the same virus that causes chickenpox. After you recover from chickenpox (or have the chickenpox vaccine), the virus does not leave your body, but continues to live in some nerve cells. For reasons that aren't totally understood, the virus can become active instead of remaining inactive. When it is activated, it produces shingles.
Anyone with the varicella-zoster virus in his or her body can be at risk for getting shingles. Right now there is no way of knowing who will get shingles disease. But, there are things that make you more likely to get shingles. These "shingles risk factors" include:

• Advanced age
• Problems with the immune system
• Chickenpox during pregnancy.

Advanced Age
About 25 percent of all adults, mostly otherwise healthy, will get shingles during their lifetime, usually after age 40. The incidence increases with age. For example, shingles is 10 times more likely to occur in adults over 60 than in children under 10.

Immune System Problems
Your immune system is the part of your body that fights off infections. Age can affect your immune system. So can an HIV infection (or AIDS), cancer, cancer drugs, radiation treatments, or an organ transplant. Even stress or a cold can weaken your immune system for a short time and put you at risk for shingles.

Chickenpox During Pregnancy
Youngsters whose mothers had chickenpox late in pregnancy -- 5 to 21 days before giving birth -- or who had chickenpox in infancy have an increased risk of pediatric shingles. Sometimes these children are born with chickenpox or develop a typical case within a few days.
What Are the Causes of Shingles?
There is only one cause of shingles (also known as herpes zoster) -- a reinfection with the varicella-zoster virus. The varicella-zoster virus that causes shingles is the same virus that causes chickenpox. The infection with this virus just tends to occur during different decades of a person's life.

The Varicella-Zoster Virus - - The "Cause of Shingles"
Varicella-zoster is part of the herpesvirus family. This group of viruses includes the herpes simplex virus (HSV) that causes cold sores, fever blisters, genital herpes (a sexually transmitted disease), and the Epstein-Barr virus involved in infectious mononucleosis.

As early as 1909, a German scientist suspected that the viruses causing chickenpox and shingles were one and the same. In the 1920s and 1930s, the case was strengthened. As part of an experiment, children were inoculated with fluid from the lesions of people with shingles. Within two weeks, about half the children came down with chickenpox. Finally, in 1958, detailed analyses of the viruses taken from people with either chickenpox or shingles confirmed that the viruses were identical.

So how does the same virus that causes chickenpox also cause shingles? To understand this, it may be helpful to understand the "reactivation" of the varicella-zoster virus.

Reactivation of the Shingles Virus Causes Shingles
After an attack of chickenpox, the varicella-zoster virus moves up into the nerves, where it settles down in an inactive form (known as a latent form). It "lies down" inside specific nerve cells (neurons) that relay information to the brain about what your body is sensing -- such as whether your skin feels hot or cold, whether you've been touched, or whether you're feeling feel pain. These nerve cells lie in clusters (ganglia) adjacent to the spinal cord and brain, and are one type of sensory neuron.

As we get older, it is possible for the varicella-zoster virus to "come alive." When this happens, the shingle virus "reactivates" and then moves down the nerves to cause symptoms of shingles. Research scientists are still trying to understand why this happens and why it happens in some people and not in others.

Although shingles is most common in people over age 50, if you have had chickenpox or the chickenpox vaccine, you are at risk for developing shingles. This disease is also more common in people with weakened immune systems from HIV infection, chemotherapy or radiation treatment, transplant operations, and stress.